Filing tool



Dec. 23, 1952 LUCHSlNGER 2,622,310

FILING TOOL Filed June 21, 1948 Patented Dec. 23, 1952 FILING TOOL Ernst Luchsinger, Zurich, Switzerland, assignor to Fibra A. G., Glarus, Switzerland Application June 21, 1948, Serial No. 34,275 In Switzerland January 29, 1948 1 Claim.

My present invention relates to a filing-tool having teeth which are arcuate in plan.

In files having a straight filing-face, as is customary in manually operated files, and teeth which in plan are cut in circular arches, the centre of the cuts is situated on the centre-line of the filing-face. The said line, therefore, represents an axis symmetry of the filing-face, and the tangents erectedat the two points of intersection of an individual tooth arc with the respective two border-lines edges) of the file-on the said arc, include an acute angle with each border line, which angles are equal inter se, while, at the point of intersection of said are and centre-line, the latter includes a right angle with the tangent drawn to the said arc.

When properly operating or manipulating such a file, the centre-zone of the filing-face or each individual arched tooth, respectively, engages the work in a vertical or substantially vertical direction. The filings produced tend to coil up cylindrically in the tooth-gaps and to get seized therein, thus clogging up the tooth-gaps so that eventually the file-teeth, in this range of the filing-face, engage the work insuificiently or no longer at all. Further, the risk is imminent that the filings seized in the working-face tear up the work-face operated on. p In the case of circular filing-discs having an annular filing-face and cut as described above, the points of intersection-formed by each arched tooth and the two circular border-lines of the filing-face-are situated on one and the same radial line passing through the centre of the filing-disc. The angles formed, at each said point of intersection, by the two tangents drawn to the intersecting arcs then are different inter se, while the two tangents drawn at the point of intersection of a tooth-arc and the circular centre-line of the filing-face, include a right angle. The filings in such a rotary file, consequently, also show a tendency of getting seized in the central working-zone of the filing-face, and there is an inherent risk of tearing up the face of the work. The danger of clogging is still further increased in that the component of force acting radially inward upon rotation of the file, prevents the filings from escaping radially outward by virtue of centrifugal action, as holds true advantageously in the outside zone of the working-face of the filingdisc. The filings produced remain in the toothgap, since the two components of force balance each other.

Since, further, each tooth must be substantially arched--in accord with the ratio of the diameters of the two concentric border-circles of the filing-face-so as to make the said two components of force as large as possible, the single tooth-gapin particularly on the radially outward circular border-line of the filing-face--becomes comparatively small. Such fact impairs the design of the tooth-profile in the border-zone of the filing-face and, therefore, decreases the filing effect.

In the file disclosed by the present invention, the said disadvantages are avoided by so disposing the teeth on the filing-face that tangentsdrawn to the arched tooth at the points of intersection of the latter and the centre-line of the filing-face on one hand, and of the arched tooth and the respective two border-lines of said face on the other handinclude acute angles with tangents drawn to the said border-lines at said points of intersection, respectively, when the filing-face is arcuate.

One form of invention is schematically shown, by way of example, in the annexed drawing, in which- The figure shows a rotary filing-disc having an annular filing-face.

In the single figure of the drawing, the annular filing-face of a rotary circular filing-disc is designated by I. Only the arcs 2, 2'--formed by the tips of the profile of two adjacent teethare shown in plan. The said arcs, e. g., may be circular arcs. The concentric border-lines of face I are designated by 3 and 4, and their radius by 6 and 1 respectively. The arrow on the center-line 5 of face I indicates the direction of rotation of the circular filing-disc. The centers of the arcs 2 and 2' are laterally ofiset with respect to the center-line 5, namely in direction towards the center of the annular disc. Tangentsdrawn at the points of intersection A, B and C of the tooth-arc and the center-line 5 or the border-lines 3 and 4, respectively, include angles of less than angle our being the largest, a2 the smallest, and a intermediate of the two.

Chords 8, 8' drawn through the points of intersection B and C of the tooth-arc 2 and, similarly, tooth-arc 2', intersect at a point situated in the space inside the radially inner border-line 3 of filing-face l.

The adaptation described of the annular filingface I causes the filingswhich coil spiral-like upon being produced when rotating the circular filing-disc--to be removed from the range of the filing-face l by virtue of the radially outward directed component forces so as to clear the filingface I. The arrangement described of the tootharcs on the filing-face I permits to flatten the said arcs in comparison with the conventional design, which leads to a correspondingly greater spacing between successive tooth-arcs within the radially inside zone of the filing-face and, therefore, permits to properly adapt the filing-teeth.

What I claim as new and desire to secure by Letters Patent, is:

A rotary tool disc for performing filing work on fixed workpieces, comprising a rotary disc provided with circularly shaped filing surfaces on its side faces, said filing surfaces being limited at their edges by inner and outer concentric circles and having arcuately shaped filing teeth, the arcs of which are of such a shape that a tangent to the are at any point would form an acute angle with a line through said point extending in the direction of rotation of the disc, and the secant lines of adjacent arcs drawn through the points of intersection of the respective arcs with the inner and outer limiting lines are divergent.

ERNST LUCHSINGER.

REFERENCES CITED The following references are of record in the file of this patent:

I UNITED STATES PATENTS Number Name Date 348,637 Raymond Sept. '7, 1886 FOREIGN PATENTS Number Country Date 138,948 Switzerland June 2, 1930 

